Disallow object/function templates when creating snapshots.

R=vogelheim@chromium.org

Review URL: https://codereview.chromium.org/791033002

Cr-Commit-Position: refs/heads/master@{#25749}

src/api.cc

@@ -802,6 +802,9 @@ Local<FunctionTemplate> FunctionTemplate::New(
     v8::Handle<Signature> signature,
     int length) {
   i::Isolate* i_isolate = reinterpret_cast<i::Isolate*>(isolate);
+  // Changes to the environment cannot be captured in the snapshot. Expect no
+  // function templates when the isolate is created for serialization.
+  DCHECK(!i_isolate->serializer_enabled());
   LOG_API(i_isolate, "FunctionTemplate::New");
   ENTER_V8(i_isolate);
   return FunctionTemplateNew(
@@ -1141,6 +1144,9 @@ Local<ObjectTemplate> ObjectTemplate::New() {
 Local<ObjectTemplate> ObjectTemplate::New(
     i::Isolate* isolate,
     v8::Handle<FunctionTemplate> constructor) {
+  // Changes to the environment cannot be captured in the snapshot. Expect no
+  // object templates when the isolate is created for serialization.
+  DCHECK(!isolate->serializer_enabled());
   LOG_API(isolate, "ObjectTemplate::New");
   ENTER_V8(isolate);
   i::Handle<i::Struct> struct_obj =